Basic Electrical Engineering: Part7

Solved Objective Questions from Basic Electric Engineering

[1] Which of the following is not  a general characteristic of ac wave?

(a)  The wave shape is identical for each cycle

(b)  The polarity reverses periodically

(c)  The electrons always flow in the same direction

(d)  There is a definite frequency

Answer: C

[2] All sine waves

(a)  Have similar general appearance

(b)  Have instantaneous rise and fall times

(c)  Are in the same phase as cosine waves

(d)  Rise instantly, but decay slowly

Answer: A

[3] The derivative of a sine wave

(a)  Is shifted in phase by ½ cycle from the sine wave

(b)  Is the rate of change in the instantaneous value

(c)  Has instantaneous rise and decay times

(d)  Rise instantly, but decays slowly

Answer: B

[4] A phase difference of 180deg in the circular motion model of a sine wave represents

(a)  ¼ revolution

(b)  ½ revolution

(c)  A full revolution

(d)  Two full revolution

Answer: B

[5] We can add or subtract a ….degrees of phase to or from a wave, and end up with exactly the same wave again

(a)  90

(b)  180

(c)  270

(d)  360

Answer: D

[6] A wave has a frequency of 300kHz. One complete cycle takes…..seconds

(a)  1.3000

(b)  0.00333

(c)  1/3000

(d)  3.33 X 10^-6

Answer: D

[7] A wave has a frequency of 440Hz, how long does it take for 10⁰ of a cycle to occur?

(a)  0.00273s

(b)  0.0000273s

(c)  0.0000631s

(d)  0.00000631s

Answer: C

[8] One waveform has a peak value of ±3V and the other has peak value of ±5V. These two waves are in phase coincidence. The resultant has voltages of

(a)  ±8Vpk, in phase with the composites

(b)  ±2 Vpk, in phase with the composites

(c)  ±8Vpk, in phase opposition with respect to the composites

(d)  ±2 Vpk, in phase opposition with respect to the composites

Answer: A

[9] Two pure sine waves that differ in phase by 180⁰ can be considered to

(a)  Be offset by two full cycles

(b)  Be in phase opposition

(c)  Be separated by less than ¼ cycle

(d)  Have a frequency of ½ cycle

Answer: B

[10] A BJT has 

(a) Three PN junctions
(b) Three semiconductor layers
(c) Two N type layers around a P type layer
(d) A low avalanche voltage

Answer: B